Fig. 4. I_soce is inactivated in eggs.

A, the same protocol outlined in the legend of Fig. 2 was used to record I_soce. Time course of I_soce activation in oocytes (circles) and eggs (triangles) in response to ionomycin (10 μm) is shown. The bars above the traces indicate ionomycin (Ionom.) and La³⁺ (La) addition (0.1 mm). Data show the current at −140 mV. B, current-voltage relationship of I_soce in oocytes and eggs. C, average I_soce at −140 mV in oocytes and eggs following store depletion with ionomycin or IP₃. The number of cells per treatment is indicated. I_{Cl, Ca} in oocytes and eggs is as follows: cells were voltage clamped using the protocol shown in D. IP₃ injection (2 pmol) is indicated by the arrow. D and E, time course of I_{Cl, Ca} development. I_Cl1 (squares) was measured as the maximal current at +40 mV, and I_Cl2 was measured as the maximal current at −140 mV as described previously (20). F, I_Cl1 was significantly larger (p < 0.00052) in eggs as compared with oocytes (n = 5).